Shares of Weight Watchers fell more than 15 percent in extended trading on Thursday after the company reported a decline in fourth-quarter sales as subscriptions fell. The weight management services provider reported a net loss of $11.3 million, or 18 cents per share, in the quarter ended Jan. 2, compared with net income of $4.4 million, or 8 cents per share, a year earlier. Active subscribers fell 4.8 percent in the quarter.

Gap shares moved lower after the bell when the retailer posted quarterly results that largely met expectations but forecast that it could face a challenging year ahead. The company reported fiscal fourth-quarter earnings of 57 cents per share, adjusted, on $4.39 billion in revenue. Analysts expected Gap to report earnings per share of 57 cents on revenue of $4.46 billion, according to Thomson Reuters consensus estimates.

"With a year of transition behind us, I'm confident that we have the right strategies in place to fuel our long-term growth," said Art Peck, Gap's chief executive officer, in a statement.

Palo Alto Networks saw shares continued to rise after hours; they got an initial boost during the regular session when the company released its earnings report earlier than it planned. The security firm reported higher-than-expected second-quarter revenue as companies and governments spent more to protect themselves from cyberattacks. Total revenue for the fiscal second quarter 2016 grew 54 percent year-over-year to a record $334.7 million, compared with total revenue of $217.7 million for the fiscal second quarter 2015.

Shares of SunEdison soared more than 25 percent after the bell on Thursday when reports surfaced that the solar-power company defeated an injunction on a deal with its yieldco, TerraForm Power. In January, David Tepper-led hedge fund Appaloosa Management sued to prevent SunEdison's yieldco from taking over some of Vivint Solar's assets after SunEdison acquires the rooftop panel installer. TerraForm is to acquire Vivint's residential solar rooftop portfolio after SunEdison completes the Vivint transaction. Appaloosa sought "immediate injunctive relief" last month, given that SunEdison's acquisition of Vivint could close "at any time," the hedge fund said in a filing in a Delaware court.

— CNBC's Christine Wang and Jacob Pramuk and Reuters contributed to this report.